Looking Up: Take in the galactic scenery

Thursday

Apr 4, 2013 at 3:35 PMApr 4, 2013 at 3:35 PM

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By Peter Becker

Managing Editor

The next clear, April evening treat yourself to a journey perhaps beyond belief. Step outside, and look up at the southeastern sky. Far behind the glittering field of stars capturing your attention, is one of the largest structures ever found, an immense collection of galaxies moving together through the Universe, bound by mutual gravitational attraction.

This is the Virgo Supercluster, one of millions of superclusters in the observable Universe. As wide as 110 million light years, the Virgo Supercluster contains around 200 "galaxy groups", approximately 2,500 large galaxies ad around 50,000 dwarf galaxies. The estimated number of stars approaches 200 trillion in this region.

Itís not only the closest supercluster, it is OUR supercluster. The Milky Way Galaxy, and several other nearby galaxies forming what we call the "Local Group", is on the outskirts.

All the thousands of stars you see at night (and the one you see by day) with your unaided eyes, are just a small portion of our own immense galaxy, the Milky Way. The good Earth is an infinitesimal speck of dust orbiting just one of approximately 200 billion stars, making up our vast spiral home.

We cannot, on human terms, begin to appreciate the colossal size of even our Milky Way, at 100,000 light years in width. Thatís how long it takes starlight from a star on one edge, to reach an observer on the opposite side.

Yet the vast Milky Wayís nearest large neighbor, the Andromeda Galaxy, is 2.5 million light years from here and that is considered close. That is roughly the distance of 25 Milky Ways, end to end.

Our galactic neighborhood, the Local Group, is a nice piece of real estate. We have around 30 neighbors and unlike many of us on Earth, we are getting to know who is next door. Astronomers have been sorting it out for hundreds of years, ever since early observations of what appeared to be wispy clouds among the nearby stars seen in the telescope, gave way to realization of their true nature. Do all our neighbors get along? We suppose so, except for the nasty detail that the Andromeda Galaxy is on a collision course with the Milk Way. Perhaps Canis Major, the Big Dog constellation, has been barking too much.

Actually, galaxies have a habit of smashing into each other and merging, sharing stars and spreading them out. Collision of galactic nebulosity, astronomers believe, lead to formation of new stars shining forth from the compressed gases.

The outer reaches of the great Virgo Supercluster contains many galaxies you can see if you have access to a backyard telescope. You can find some with even a small telescope having a three inch lens or main mirror, though larger telescopes show more. They appear in the telescope as small, dim, fuzzy patches, some round, others oval or even needle-shaped. Many star atlases are available detailing positions of the galaxies among the faint foreground stars.

Without even leaving your yard, you can shift your telescope just a few inches as you scan with your eyepiece, and travel from one of these galaxies to the next. You are covering millions of light years with this change of angle by merely pushing the telescope tube with your hand.

New Moon is on April 10. That means dark, moon-less evening skies all week.